NRF24L01+ : Can't Read RF_CH register ?

[PythonNerd]

Hi

i am new with nr24L01 module , i am currently trying to configure them but , i am not able to read the RF_CH register just after write into it ? so i don't know if the write effectvely occurs ?

i have try with the EN_AA register and i have no problem to write it and read it !! 

So maybe the RF_CH registers is read only ? or did i need to complete some conditions before writing/reading it ?

PS : i wait one second between write and read sequence

i join picture of my logic analyser , maybe someone will find what is wrong , thx in advance

regards

[Håkon Alseth]

Looks like your SPI mode is incorrect. You can see this because your MISO and MOSI lines do not align bit-wise (they differ by half a CLK cycle).

The nRF24L01+ expects SPI mode 0 (CPOL=0, CPHA=0).

See wiki for more info:

https://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus#Clock_polarity_and_phase

Cheers,

Håkon

[PythonNerd]

First thanks for your answer , i will try to investigate my SPI bus mode i just need some précision :

for MOSI :

did the nrf24 sample the bit at Rising edge of clock or failling edge ?

for MISO :

must i sample the bit at the failing edge or at the the middle of SCK pulse ??

regards

pierre

[Håkon Alseth]

Hi,

PythonNerd said:

did the nrf24 sample the bit at Rising edge of clock or failling edge ?

CPHA = 0, samples on falling.

PythonNerd said:

must i sample the bit at the failing edge or at the the middle of SCK pulse ??

It's easier to see in this diagram: https://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus#/media/File:SPI_timing_diagram2.svg

It's the blue line.

For more timing information about the SPI interface to the nRF24L01+, please see the datasheet chapter 8.3.1

Cheers,

Håkon